RE: Getting temperature from DS18B20 with nRF5340-DK

Elfving — Wed, 13 Jul 2022 14:27:10 GMT

Great! I am glad to hear it. And no problem at all.

And great that you've contributed by adding your code and solution here, so that it may help others down the line. It seems that there is a lot of people on DevZone that have been struggling with the same thing as you.

Regards,

Elfving

RE: Getting temperature from DS18B20 with nRF5340-DK

Sulian — Wed, 13 Jul 2022 07:21:01 GMT

Hello Elfving,

I looked at my signal with an oscilloscope and the issue was indeed the fault of k_sleep(K_USEC(timeout)) which couldn't apparently work with microseconds (same problem with k_usleep(timeout)).

I have seen somewhere that upgrading the value of CONFIG_SYS_CLOCK_TICKS_PER_SEC could have helped but the default value seems to already be the highest for nRF5340 (32768).

So I tried to use timers :

K_TIMER_DEFINE(timer, NULL, NULL);

/* Do some work */

/* When a 15 usec wait is needed */
k_timer_start(&timer, K_USEC(15), K_NO_WAIT);

/* Wait the end of the timer */
k_timer_status_sync(&timer);

/* Continue the work */

But it wasn't working under a hundred of microseconds nor precise.

At this moment I didn't see the k_busy_wait function so I made my own timer function :

void timer(uint64_t iTimeout)
{
    uint64_t iUptime = k_uptime_ticks();

    while ((k_uptime_ticks() - iUptime) < k_us_to_ticks_near64(iTimeout));
    
}

And it works nicely.

I tried replacing my timer function with k_busy_wait and it's still working perfectly !

Thanks you very much Eflving !

If someone is interesting by my code, here it is :

(I made it board agnostic by replacing the nrf_gpio function, and the k_busy_wait functions can be replace by the timer function).

#include <kernel.h>
#include <drivers/gpio.h>

#include "ds18b20.h"

// #define DS_PIN 26
#define DS_PIN 10

// Commands
#define STARTCONVO      0x44
#define READSCRATCH     0xBE
#define WRITESCRATCH    0x4E

// Scratchpad locations
#define TEMP_LSB        0
#define TEMP_MSB        1

// Device resolution
#define TEMP_9_BIT  0x1F //  9 bit
#define TEMP_10_BIT 0x3F // 10 bit
#define TEMP_11_BIT 0x5F // 11 bit
#define TEMP_12_BIT 0x7F // 12 bit

typedef uint8_t ScratchPad[9];

const struct device * dev;

/**@brief Custome timer.
 */
void timer(uint64_t iTimeout)
{
    uint64_t iUptime = k_uptime_ticks();

    while ((k_uptime_ticks() - iUptime) < k_us_to_ticks_near64(iTimeout));
    
}


/**@brief Function for sending one bit to bus.
 */
void ds18b20_send(char bit)
{
    dev = device_get_binding("GPIO_0");
    gpio_pin_configure(dev, DS_PIN, GPIO_OUTPUT_INACTIVE);

    
    k_busy_wait(5);

    if(bit==1)
        gpio_pin_set(dev, DS_PIN, 1);
    
    k_busy_wait(80);
    
    gpio_pin_set(dev, DS_PIN, 1);
}


/**@brief Function for reading one bit from bus.
 */
unsigned char ds18b20_read(void)
{
    unsigned char presence=0;

    dev = device_get_binding("GPIO_0");
    gpio_pin_configure(dev, DS_PIN, GPIO_OUTPUT_INACTIVE);

    k_busy_wait(2);

    gpio_pin_set(dev, DS_PIN, 1);
    k_busy_wait(15);

    gpio_pin_configure(dev, DS_PIN, GPIO_INPUT);

    if(gpio_pin_get(dev, DS_PIN))
        presence = 1;
    
    else
        presence = 0;
    
    
    return presence;
}


/**@brief Function for sending one byte to bus.
 */
void ds18b20_send_byte(char data)
{
    unsigned char i;
    unsigned char x;

    for(i=0;i<8;i++)
    {
      x = data>>i;
      x &= 0x01;
      ds18b20_send(x);
    }

    k_busy_wait(100);
}


/**@brief Function for reading one byte from bus.
 */
unsigned char ds18b20_read_byte(void)
{
    unsigned char i;
    unsigned char data = 0;

    for (i=0;i<8;i++)
    {
        if(ds18b20_read()) data|=0x01<<i;
        k_busy_wait(15);
    }

    return(data);
}


/**@brief Function for sending reset pulse.
 */
unsigned char ds18b20_reset(void)
{
    unsigned char presence;

    dev = device_get_binding("GPIO_0");
    gpio_pin_configure(dev, DS_PIN, GPIO_OUTPUT_INACTIVE);

    k_busy_wait(500);
    
    gpio_pin_set(dev, DS_PIN, 1);

    gpio_pin_configure(dev, DS_PIN, GPIO_INPUT);
    k_busy_wait(30);


    if(gpio_pin_get(dev, DS_PIN) == 0)    
        presence = 1;   
    else    
        presence = 0;
    
    k_busy_wait(470);

    if(gpio_pin_get(dev, DS_PIN) == 1)    
        presence = 1;   
    else  
        presence = 0;

    return presence;
}


/**@brief Function for reading temperature.
 */
float ds18b20_get_temp(void)
{
    unsigned char check;
    char temp1=0, temp2=0;

    check=ds18b20_reset();
    
    if(check)
    {
        ds18b20_send_byte(0xCC);
        ds18b20_send_byte(0x44);

        k_busy_wait(600);

        check=ds18b20_reset();
        ds18b20_send_byte(0xCC);
        ds18b20_send_byte(0xBE);

        temp1=ds18b20_read_byte();
        temp2=ds18b20_read_byte();

        check=ds18b20_reset();

        float temp=0;
        temp=(float)(temp1+(temp2*256))/16;

        return temp;
    }
      return 0;
}


/**@brief Function for reading bit.
 */
uint8_t OneWire_read_bit(void)
{
    uint8_t r;

    dev = device_get_binding("GPIO_0");
    gpio_pin_configure(dev, DS_PIN, GPIO_OUTPUT_INACTIVE);

    k_busy_wait(3);

    gpio_pin_configure(dev, DS_PIN, GPIO_INPUT);

    k_busy_wait(10);

    r = gpio_pin_get(dev, DS_PIN);

    k_busy_wait(53);

    return r;
}


/**@brief Function for reading.
 */
uint8_t OneWire_read()
{
    uint8_t bitMask;
    uint8_t r = 0;

    for (bitMask = 0x01; bitMask; bitMask <<= 1)
	    if ( OneWire_read_bit()) r |= bitMask;
    
    return r;
}


/**@brief Function for reading scratchpad value
 */
void ds18b20_readScratchPad(uint8_t *scratchPad, uint8_t fields)
{
    ds18b20_reset();

    ds18b20_send_byte(0xCC);
    ds18b20_send_byte(READSCRATCH);

    for(uint8_t i=0; i < fields; i++)
        scratchPad[i] = OneWire_read();
    
    ds18b20_reset();
}


/**@brief Function for request temperature reading
 */
void ds18b20_requestTemperatures(void)
{
    ds18b20_reset();
    ds18b20_send_byte(0xCC);
    ds18b20_send_byte(STARTCONVO);
}


/**@brief Function for reading temperature method 2
 */
float ds18b20_get_temp_method_2(void)
{
    ds18b20_requestTemperatures();

    ScratchPad scratchPad;
    ds18b20_readScratchPad(scratchPad, 2);

    int16_t rawTemperature = (((int16_t)scratchPad[TEMP_MSB]) << 8) | scratchPad[TEMP_LSB];
    float temp = 0.0625 * rawTemperature;

    return temp;
}


/**@brief Function for setting temperature resolution
 */
void ds18b20_setResolution(uint8_t resolution)
{
    ds18b20_reset();

    ds18b20_send_byte(0xCC);
    ds18b20_send_byte(WRITESCRATCH);
    
    // two dummy values for LOW & HIGH ALARM
    ds18b20_send_byte(0);
    ds18b20_send_byte(100);

    switch (resolution)
    {
        case 12:
            ds18b20_send_byte(TEMP_12_BIT);
            break;

        case 11:
            ds18b20_send_byte(TEMP_11_BIT);
            break;

        case 10:
            ds18b20_send_byte(TEMP_10_BIT);
            break;

        case 9:
        default:
            ds18b20_send_byte(TEMP_9_BIT);
            break;
    }

    ds18b20_reset();
}

Thanks you again Elfving !

Regards,

Sulian

RE: Getting temperature from DS18B20 with nRF5340-DK

Elfving — Tue, 12 Jul 2022 14:20:29 GMT

Hello again Sulian, thank you for your patience

[quote user=""]Im am using two different sources I found on internet [/quote]

Just in case you didn't notice: the first code snippet that you've found here is based on the nRF5 SDK, it might not work on NCS straight out of the box. But it seems that there are other people in devzone who has been in your shoes before and tried to migrate it to NCS.

[quote user=""]

What I observe is that, during the reading part, it only reads high state values (=0xFF).

[/quote]

Yeah, it might be that it isn't connected correctly though it is hard to say where the issue is exactly. Do you have a logic analyzer?

Interestingly enough, the case I linked you to ran into a similar issue. Replacing his k_usleep with k_busy_wait() ended up fixing it for him. Does that help in your case?

Regards,

Elfving

RE: Getting temperature from DS18B20 with nRF5340-DK

Sulian — Fri, 08 Jul 2022 07:20:15 GMT

Hello everyone,

I come here with some news.

I have tested the sensor with an Arduino Uno, by following this tuto : https://create.arduino.cc/projecthub/TheGadgetBoy/ds18b20-digital-temperature-sensor-and-arduino-9cc806

Here a pic of the hard :

And it works perfectly. So I am pretty sure the issue with the nRF5340 comes from the soft.

Regards,

Sulian

RE: Getting temperature from DS18B20 with nRF5340-DK

Sulian — Thu, 07 Jul 2022 14:01:04 GMT

Hello Elfving,

Thanks you very much. It's okay don't worry.

I also keep trying on my side and come here if I have any updates.

Regards,

Sulian

RE: Getting temperature from DS18B20 with nRF5340-DK

Elfving — Thu, 07 Jul 2022 13:50:39 GMT

Hello Sulian,

I am looking into it. Note that we have entered the summer holiday period in Norway so staffing is low, some delayed response time should be expected.

Regards,

Elfving